Williams will face Angelique Kerber or Varvara Lepchenko, who played in Saturday's second semifinal.
Petkovic was trying to become the ninth player and first since 2010 to beat both Venus and Serena Williams in the same tournament. Petkovic eliminated Venus Williams in the quarterfinals Friday.
Record U.S. crowd sees ManU win in MI
Soccer • Ashley Young scored twice in the first half, and Manchester United beat Real Madrid 3-1 on Saturday in Ann Arbor, Mich., in front of the largest crowd to see a soccer game in the United States.
United remained unbeaten in this year's International Champions Cup, advancing to the final of the preseason tournament under new manager Louis van Gaal. Javier Hernandez added a goal in the second half for the English power.
The crowd of 109,318 at Michigan Stadium broke the previous U.S. mark of 101,799, set at the Rose Bowl for the 1984 Olympic final.
United will face Liverpool in the final in Miami on Monday night. Liverpool beat AC Milan 2-0 in the other semifinal, in Charlotte, N.C.
Canadiens, Subban sign 8-year deal
NHL • The Montreal Canadiens have agreed to terms with defenseman P.K. Subban on an eight-year deal. A day after an arbitration hearing that would have led to a one-year contract, the team and Subban reached accord Saturday on a long-term arrangement.
Subban would be under contract through the age of 33. He had 10 goals and 43 assists last season, and has 42 goals and 125 assists in his NHL career.
Bourdais earns pole at Mid-Ohio course
Auto racing • Sebastien Bourdais got through rainy conditions in IndyCar qualifying Saturday in Lexingon, Ohio, at Mid-Ohio Sports Car Course and earned his second pole position of the season.
A midday storm dampened the track and shook up qualifying. Series points leader Helio Castroneves and four-time Mid-Ohio winner Scott Dixon failed to get out of the first round.
For Bourdais, of KVSH Racing, it is his 33rd career IndyCar pole, tying him for seventh on the career list with Dario Franchitti.
The veteran from France won from the pole this season in the first race at Toronto. Ten drivers have won poles through 15 races this year.
From wire reports